Technical Specification for PVC Membrane Seepage Control in Jiangpinghe Hydropower Station Dam Face

I. Project Overview and Background

1.1 General Project Description

The Jiangpinghe Hydropower Station is the leading cascade hydropower station planned on the Loushui River, ranking as a key provincial-level project in Hubei Province. Located in Zouma Town, Hefeng County, Enshi Prefecture, Hubei Province, this hydropower station has a total installed capacity of 450 MW, with an annual power generation of 960 million kWh (1). The reservoir operates at a normal storage level of 470 meters, holding a total reservoir capacity of 1.366 billion cubic meters. The project serves multiple purposes including power generation, flood control, irrigation, navigation, tourism, and poverty alleviation, benefiting over 220,000 people of various ethnic groups in Hefeng County, Enshi Prefecture, Hubei Province (1).

The centerpiece of the Jiangpinghe Hydropower Station is its concrete face rockfill dam (CFRD), standing as the third tallest CFRD globally and the tallest under construction worldwide, with a maximum dam height of 219 meters (1). The dam crest elevation reaches 476.00m, with a crest width of 10.00m and a crest length of 414.00m. The upstream slope ratio is 1:1.4, while the downstream integrated slope ratio is 1:1.4 (with local areas at 1:1.36), featuring four tiers of access roads each 2.0m wide (1). Given the extraordinary height of this dam, the seepage control system faces unprecedented challenges, necessitating the application of advanced materials and technologies to ensure long-term safety and stability.

1.2 Construction History and Challenges

The construction journey of the Jiangpinghe Hydropower Station has been marked by significant challenges. Initially developed by Hubei Huaqing Electric Power Co., Ltd., the project came to a halt in 2011 due to funding shortages (1). In 2015, Hubei Energy Group successfully acquired the project assets through a public auction and established Hubei Energy Group Loushui Hydropower Co., Ltd. to oversee the comprehensive construction and operational management of the hydropower station. Full 复工 of the project commenced on August 29, 2015 (1).

One of the primary challenges encountered during the 复工 phase was the substandard quality of the cushion material used in the original dam construction. To ensure the dam's seepage control performance, designers made the strategic decision to adopt PVC membrane seepage control technology for the face slab rockfill dam above the 200-meter elevation (1). This decision was based on the proven advantages of PVC materials in high dam seepage control applications, particularly their exceptional deformation adaptability and superior seepage prevention capabilities.

Additionally, prior to the 复工，the project's planning and design depth was insufficient, resulting in a critical situation where no access roads were available once the dam body had been filled to the 400-meter elevation. After extensive research, a decision was made to construct an additional access road on the left bank of the dam, which was successfully completed and opened to traffic in October 2017, ensuring that the dam filling construction progress remained unaffected (1).

1.3 Application Background of PVC Seepage Control Technology

The application of PVC membrane seepage control technology in the Jiangpinghe Hydropower Station project has a specific background. Due to quality defects in the already constructed works before the 复工，particularly the substandard quality of the dam cushion material, PVC membrane seepage control technology was adopted for the face slab rockfill dam above the 200-meter elevation to enhance the dam's seepage control performance (1).

In practical application, a 2.5mm thick PVC composite geomembrane was laid on the concrete face slab surface below elevation 380m of the Jiangpinghe Hydropower Station dam as an auxiliary seepage control system. Below elevation 380m, a clay blanket and ballast material were provided. When the dam requires maintenance, the reservoir water level can be lowered to elevation 378m. Therefore, the top of the geomembrane is located at elevation 380m (with the port sealing area between elevations 380m and 382m) (1).

Above elevation 380m, the geomembrane extends to the dam crest at the vertical joints and peripheral joints of the face slab. Both sides of the joints are sealed and fixed. The perimeter of the geomembrane is sealed and fixed to the toe slab, and across the joints, the geomembrane on both sides is welded together to form a continuous seepage control system (1).

This PVC seepage control system has achieved remarkable results. Under the condition of a reservoir water level at elevation 460m, the total seepage volume through the geomembrane below elevation 382m (corresponding to a maximum water head of 197m) is 5.3L/s. Without the geomembrane reinforcement, the corresponding seepage volume would be 13.2L/s, clearly demonstrating the significant seepage control effect (1). The project saved 10.27 million yuan in engineering investment and created economic benefits of 16 million yuan (1).

II. Technical Principles and Material Properties of PVC Seepage Control Technology

2.1 Basic Principles of PVC Seepage Control Technology

PVC (Polyvinyl Chloride) seepage control technology creates a continuous seepage prevention barrier on the dam surface using the low permeability and high toughness of PVC materials, preventing water infiltration. The seepage prevention principle of PVC materials is mainly based on the following aspects:

1. Molecular Structure Compactness: PVC materials feature a dense molecular structure with almost complete impermeability to water. Their permeability coefficient can reach the level of 10-12 cm/s, which is much lower than materials such as clay, gravel soil, and asphalt concrete used for seepage control. This characteristic makes PVC an ideal seepage prevention material (3).
2. Material Flexibility: PVC materials exhibit excellent elasticity and deformation adaptability, capable of withstanding different construction conditions and working stresses. This flexibility makes them particularly suitable for application in high dams that may experience deformation, such as the 219-meter-high face slab rockfill dam of the Jiangpinghe Hydropower Station (3).
3. Joint Treatment Technology: The PVC seepage control system processes joints through heat welding or bonding techniques to ensure seamless connection and prevent seepage. The double-weld technique not only ensures connection strength but also allows for inflation testing through the intermediate cavity to guarantee welding quality (12).
4. Integrated Seepage Control System: The PVC seepage control system is not merely a single seepage prevention membrane but also includes auxiliary structures such as anchoring systems and protective layers to form a complete seepage control system. In the Jiangpinghe Hydropower Station, there are 11 connection procedures between the PVC membrane and the dam face slab, ensuring a tight bond between the PVC membrane and the dam body (1).

2.2 Material Properties of PVC Used in Jiangpinghe Project

The PVC composite geomembrane used in the Jiangpinghe Hydropower Station has the following characteristics:

1. Material Specifications: The Jiangpinghe Hydropower Station employs a 2.5mm thick PVC composite geomembrane, specifically designated as "2.5/500", meaning a 2.5mm thick PVC membrane with 500g/m² geotextile on each side. This structure combines the high strength of geotextile with the seepage prevention performance of PVC membrane, creating a geomembrane with excellent performance (1).
2. Physical and Mechanical Properties:
   • Tensile Strength: PVC materials exhibit high tensile strength, capable of withstanding tensile stresses generated by dam deformation.
   • Elongation at Break: PVC materials have high elongation at break, able to adapt to dam deformation without 破裂.
   • Puncture Resistance: Due to the composite geotextile, the PVC composite membrane has high puncture resistance, effectively resisting punctures from sharp objects.
   • Tear Resistance: PVC materials have good tear resistance, able to withstand tearing forces caused by uneven settlement of the dam (3).
3. Chemical Stability: PVC materials exhibit excellent chemical corrosion resistance and aging resistance, maintaining stable physical properties under various environmental conditions. This characteristic ensures the long-term effectiveness of the PVC seepage control system (7).
4. Weather Resistance: PVC materials have good weather resistance, able to withstand the effects of natural factors such as ultraviolet radiation and temperature changes. In the high-altitude, large temperature difference environment of the Jiangpinghe Hydropower Station, this characteristic is particularly important (7).

2.3 Composition and Structure of PVC Seepage Control System

The PVC seepage control system of the Jiangpinghe Hydropower Station mainly consists of the following components:

1. PVC Composite Geomembrane: As the core seepage control layer, it directly prevents water infiltration. The Jiangpinghe Hydropower Station employs a two-cloth-one-membrane structured PVC composite geomembrane composed of 500g/m² geotextile + 2.5mm PVC membrane + 500g/m² geotextile (1).
2. Anchoring System: Used to fix the position of the PVC membrane, preventing it from shifting under water pressure. The anchoring system typically includes stainless steel angle bar pressure strips, rubber gaskets, stainless steel expansion bolts, and weather-resistant sealant. In the Jiangpinghe Hydropower Station, there are 11 connection procedures between the PVC membrane and the dam face slab, ensuring a tight bond between the PVC membrane and the dam body (1).
3. Joint System: PVC membranes are connected by heat welding to form a monolithic structure. The Jiangpinghe project employs a double-weld technique, with each weld 10mm wide and a 10mm cavity left between the two welds for detecting welding quality (12).
4. Protection Layer: To protect the PVC membrane from external damage, a protection layer is set on the surface of the PVC membrane. The Jiangpinghe Hydropower Station has set a clay blanket and ballast material on the PVC membrane (1).
5. Monitoring System: Used to monitor the working status of the PVC seepage control system, promptly identifying potential problems. Monitoring data from the Jiangpinghe Hydropower Station shows that under the condition of a reservoir water level at elevation 460m, the total seepage volume through the PVC seepage control system below elevation 382m is 5.3L/s, demonstrating remarkable seepage control effects (1).

This complete PVC seepage control system structure ensures the seepage control safety of the high dam of the Jiangpinghe Hydropower Station, providing a reliable guarantee for the safe operation of the project.

III. Construction Technology and Process of PVC Seepage Control in Jiangpinghe Hydropower Station

3.1 Pre-construction Preparations

Pre-construction preparations for PVC seepage control construction in the Jiangpinghe Hydropower Station mainly include the following aspects:

1. Technical Preparations:
   • Organize all participating parties to conduct technical disclosure on the key and difficult points in PVC construction
   • Invite manufacturer technical personnel to provide on-site guidance and quality control
   • Conduct construction tests, and jointly study and explore difficult construction techniques
   • Develop detailed construction technical plans and quality control standards (12)
2. Material Preparations:
   • Conduct sampling inspection on the PVC composite geomembrane delivered to the site, with a sampling rate of more than 5% of the delivered rolls
   • Check product qualification certificates and factory inspection reports
   • Ensure materials are covered or packaged during transportation and storage to avoid direct sunlight
   • Store materials away from ignition sources, with a storage period not exceeding 1 year (12)
3. Site Preparations:
   • Clean the dam surface to ensure no debris or sharp objects are present
   • Treat the concrete face slab surface to ensure it is 平整，with no honeycombs, pitted surfaces, sanding, or pits
   • If defects are found, use SR waterstop material for leveling
   • Conduct surveying and setting out to determine the laying position and scope of the PVC membrane (12)
4. Equipment Preparations:
   • Prepare specialized construction equipment such as heat welding machines and inflation detection equipment
   • Check whether equipment is in normal condition and meets construction requirements
   • Prepare welding materials and auxiliary tools (12)

In pre-construction preparations for the Jiangpinghe Hydropower Station, particular attention was paid to technical disclosure and construction testing to ensure that construction personnel were familiar with the technical requirements and operating points of PVC seepage control, laying a foundation for the smooth progress of subsequent construction.

3.2 Construction Process of PVC Seepage Control Face Slab

The construction process of the PVC seepage control face slab for the Jiangpinghe Hydropower Station mainly includes the following steps:

1. Base Treatment:
   • Clean the dam base to ensure no debris or sharp objects are present
   • Treat the concrete face slab surface to ensure it is 平整
   • Check with a 2m straightedge, with unevenness not exceeding 5mm
   • For existing honeycombs, pitted surfaces, sanding, pits, etc., level with SR waterstop material (12)
2. Laying of PVC Composite Geomembrane:
   • Lay the PVC composite geomembrane according to design requirements
   • Adopt a wavy loose laying method with a surplus of about 1.5% to prevent stress concentration and facilitate splicing
   • After spreading, promptly flatten and spread out the membrane, requiring the PVC membrane to fit 平整 with the contact surface, without protrusions or wrinkles
   • For vertical installations, first fix the geomembrane with steel brackets to meet the design steep slope requirements
   • Adjust the welding edge distance between the upper and lower PVC composite geomembranes to ensure a lap width of more than 10cm (12)
3. Welding of PVC Membrane:
   • Peel off the geotextile on the PVC composite geomembrane at the weld seam, blow away sand, dirt, and other contaminants from the membrane surface
   • Clean the welding parts of the upper and lower PVC membranes with acetone as a cleaning agent to ensure the PVC membrane surface is clean
   • Select a heat welding machine for PVC membrane welding
   • Conduct test welding before formal welding, controlling the walking speed at 0.9~1.2m/s during operation, and the test welding temperature at 410~450°C
   • Adopt double-weld welding, each 10mm wide, with a 10mm cavity left between the two welds
   • After welding, check the quality of each weld (12)
4. Weld Inspection:
   • Use visual inspection to check for missed welds on the PVC membrane, whether the welds are burnt, whether there are wrinkles, and whether the splicing is uniform
   • Use inflation testing to inspect each weld: seal both ends of the tested welding section, insert an air needle into the cavity between the two welds, inflate to 0.05MPa, then observe quietly for 30 seconds. If the air pressure does not drop, it indicates no leakage and the weld is qualified
   • Promptly repair any detected problems (12)
5. Weld Reinforcement Treatment:
   • After welding, apply modified acrylic adhesive to the outside of the weld to bond the non-welded parts of the PVC membrane joints, enhancing joint strength
   • Use a portable bag-sealing machine to sew the geotextile on both sides of the PVC membrane, connecting the upper and lower geotextiles into a whole (12)
6. Anchoring Treatment:
   • The PVC membrane of the Jiangpinghe Hydropower Station is anchored at elevation 380m, with the port sealing area between elevations 380m and 382m
   • Adopt stainless steel angle bar pressure strips, rubber gaskets, stainless steel expansion bolts, etc., for anchoring
   • The tightening of expansion bolts is carried out in three stages, with a 2-day interval between the second and first tightening, and the final tightening should be carried out before adding clay or fine sand blanket and before reservoir impoundment
   • After anchoring, seal the gap between the pressure strip, the end of the geomembrane, and the cutoff wall with weather-resistant sealant to improve seepage control quality (1)
7. Protective Layer Construction:
   • After laying the PVC composite geomembrane, promptly backfill the protective layers on both sides of the membrane
   • The Jiangpinghe Hydropower Station has set a clay blanket and ballast material as protective layers below elevation 380m
   • Conduct layered and synchronous balanced backfilling of the protective layer to avoid excessive lateral pressure on one side damaging the geomembrane
   • Trim the protective layer manually with mechanical assistance to ensure it meets design requirements (1)

During the construction process of the PVC seepage control face slab for the Jiangpinghe Hydropower Station, operations were carried out in strict accordance with the above procedures, with particular attention paid to welding quality and anchoring treatment to ensure the reliability of the PVC seepage control system.

3.3 Quality Control and Acceptance Standards

Quality control and acceptance for PVC seepage control construction in the Jiangpinghe Hydropower Station mainly include the following aspects:

1. Material Quality Control:
   • The performance indicators of the PVC composite geomembrane should meet design requirements and relevant standard provisions
   • Conduct sampling inspection on the PVC composite geomembrane delivered to the site to ensure the materials are qualified
   • Check quality certification documents such as product qualification certificates and factory inspection reports (12)
2. Construction Process Quality Control:
   • Base treatment quality control: Check whether the base treatment meets requirements and whether the surface 平整度 meets specifications
   • Laying quality control: Check whether the PVC membrane is laid 平整，without wrinkles or 空鼓 defects
   • Welding quality control: Check whether welding temperature, speed, and other parameters meet requirements, and whether the welds are uniform and continuous
   • Anchoring quality control: Check whether the layout of anchor points is reasonable and whether the anchoring is firm
   • Protective layer quality control: Check whether the material, thickness, and construction quality of the protective layer meet design requirements (12)
3. Quality Inspection Methods:
   • Visual Inspection: Observe the laying quality and welding quality of the PVC membrane through the naked eye
   • Inflation Detection: Conduct inflation testing on each weld to ensure no leakage in the welds
   • Peel Test: Conduct sampling inspection on welding strength to ensure welding quality
   • Destructive Test: Conduct destructive tests on the welding quality of key parts to evaluate welding strength (12)
4. Acceptance Standards:
   • Weld Quality Standard: During inflation testing, if the air pressure does not drop significantly within 30 seconds, it is considered qualified
   • Laying Quality Standard: The PVC membrane should be laid 平整，without wrinkles or 空鼓，with a lap width of not less than 10cm
   • Anchoring Quality Standard: Anchor points should be evenly distributed, firmly anchored, and tightly sealed
   • Overall Seepage Control Effect Standard: Under design water head conditions, seepage volume should be less than the design allowable value. In the Jiangpinghe Hydropower Station, under the condition of a reservoir water level at elevation 460m, the total seepage volume through the PVC seepage control system below elevation 382m is 5.3L/s, meeting design requirements (1)
5. Quality Records and Evaluation:
   • Complete various quality records during construction, including material inspection records, construction records, inspection records, etc.
   • Evaluate construction quality, with the evaluation results meeting design requirements and relevant standard provisions
   • Organize complete quality acceptance materials as the basis for project acceptance (12)

During the PVC seepage control construction process for the Jiangpinghe Hydropower Station, quality control standards were strictly implemented, and a third-party testing unit with qualified qualifications and rich experience was entrusted to conduct dynamic supervision of project quality, ensuring the construction quality of the PVC seepage control system.

IV. Comparative Analysis of PVC Seepage Control and Other Seepage Control Technologies

4.1 Analysis of Asphalt Concrete Seepage Control Technology

4.1.1 Technical Principles and Structure of Asphalt Concrete Seepage Control

Asphalt concrete seepage control technology utilizes the low permeability and good deformation performance of asphalt concrete to form a seepage control layer on the dam surface, preventing water infiltration. Its technical principles are mainly based on the following points:

1. Seepage Control Mechanism of Asphalt Concrete: During the compaction process of hot-mixed asphalt mixture, asphalt at high temperature acts as a lubricant due to its low viscosity, making it easier for mineral particles to move during rolling, resulting in a rearrangement of mineral particle positions while extruding air trapped in the mixture. Through compaction, the bulk density of the mixture increases significantly, forming asphalt concrete with the necessary density, strength, and water resistance (2).
2. Structural Composition: Asphalt concrete seepage control structures typically consist of a sealing layer, seepage control layer, leveling binder layer, and capping layer. The sealing layer is brushed with asphalt mastic, with a thickness of 2-3mm; the seepage control layer, leveling binder layer, and capping layer are paved with asphalt concrete. The thickness of the seepage control layer and capping layer is generally 8-10cm; the thickness of the leveling binder layer is determined by filling the rock base surface (2).
3. Working Performance: Asphalt concrete has good flexibility and adhesion, capable of adapting to large deformations (such as frost heave and foundation settlement deformation) without cracking. Meanwhile, although asphalt is an organic material, its aging is not severe and can be used for 30 years (2).

4.1.2 Construction Technology of Asphalt Concrete Seepage Control

The construction technology of asphalt concrete seepage control mainly includes the following steps:

1. Construction Preparations:
   • Raw material preparation: Prepare asphalt, aggregate, filler, and other raw materials, and conduct quality inspections
   • Construction equipment preparation: Prepare asphalt concrete mixing, transportation, paving, rolling, and other equipment
   • Base treatment: Clean and treat the dam surface to ensure it is 平整 and clean (2)
2. Asphalt Concrete Preparation:
   • Mix asphalt concrete according to the design mix ratio
   • Control the mixing temperature of the asphalt mixture, generally controlled above 170°C
   • Ensure the uniformity and quality stability of the asphalt mixture (2)
3. Paving and Rolling:
   • The asphalt concrete face slab is paved in layers, with strip-shaped flow operations
   • Paving temperature control: Modified asphalt concrete for the seepage control layer has a paving temperature of 150-180°C, and asphalt concrete for the leveling binder layer has a paving temperature of 140-170°C
   • Rolling control: Initial rolling temperature controlled at about 140°C, secondary rolling temperature controlled at about 110°C, final rolling temperature not lower than 90°C
   • Rolling passes control: Initial rolling 2 passes (static rolling), secondary rolling 6 passes (front vibration, rear static), final rolling 2 passes (static rolling) (2)
4. Sealing Layer Construction:
   • After the asphalt concrete face slab construction is completed, brush an asphalt mastic sealing layer on the surface
   • The thickness of the sealing layer is generally 2mm (2)
5. Joint Treatment:
   • Asphalt concrete construction joints are divided into cold joints and hot joints (joints with a temperature above 90°C are hot joints, those below 90°C are cold joints)
   • Treatment method for cold joints: First clean the debris on the joints, then apply a layer of cold asphalt coating, and then use an infrared heater for heating, raising the temperature of the heated cold joints to about 70°C
   • For hot joints between 139-90°C, before paving construction, use an infrared heater for heating, with the heating range typically being the joint surface and the adjacent 10cm horizontal area
   • For hot joints above 140°C, the rolling method is the same as the ordinary area (2)

4.1.3 Analysis of Advantages and Disadvantages of Asphalt Concrete Seepage Control

Advantages:

1. Good Seepage Control Effect: Generally can reduce seepage loss by 90%-95%, with a daily seepage volume of 0.04-0.14m³ per square meter
2. Strong Deformation Adaptability: Has good flexibility and adhesion, can adapt to large deformations without cracking
3. Good Durability: Asphalt material aging is not severe, can be used for 30 years
4. Relatively Low Cost: About 70% of the cost of concrete canal seepage control
5. Relatively Simple Construction: Construction technology is relatively mature, and construction equipment has strong versatility
6. Easy to Repair: After detecting seepage, repair is relatively easy (2)

Disadvantages:

1. Strict Construction Technology Requirements: The construction of asphalt concrete has strict requirements for temperature control, and construction quality is greatly affected by weather conditions
2. Vegetation Penetration Problem: In the long-term use process, it may face the problem of plant root penetration
3. High Construction Temperature Requirements: Construction is difficult in low-temperature environments, and construction is not suitable when the daily average temperature is below 5°C
4. Large Engineering Quantity: Compared with PVC seepage control technology, asphalt concrete seepage control requires laying a thicker structural layer, resulting in larger engineering quantities
5. Long Construction Period: There are many construction procedures, and the construction period is relatively long
6. High Maintenance Costs: As the service life increases, regular maintenance and repair are needed (2)

4.2 Analysis of Composite Geomembrane Seepage Control Technology

4.2.1 Technical Principles and Structure of Composite Geomembrane Seepage Control

Composite geomembrane seepage control technology utilizes the low permeability of geomembrane and the high strength characteristics of geotextile to form a seepage prevention barrier on the dam surface. Its technical principles are mainly based on the following points:

1. Seepage Control Principle: The geomembrane part in the composite geomembrane has an extremely low permeability coefficient (≤10-12 cm/s), effectively preventing water infiltration; the geotextile part provides reinforcement, improving overall strength and puncture resistance (3).
2. Structural Composition: Composite geomembranes mainly have two structural forms:
   • Two-cloth-one-membrane: Composed of two layers of geotextile sandwiching one layer of geomembrane, the outer geotextile has good wear resistance and puncture resistance, protecting the middle geomembrane
   • One-cloth-one-membrane: Composed of one layer of geotextile and one layer of geomembrane, relatively lighter and more suitable for environments with relatively simple stress conditions (3)
3. Working Performance: Composite geomembranes have high tensile strength, tear resistance, and puncture resistance, capable of adapting to certain deformations without 破裂. Meanwhile, the geomembrane part has excellent seepage control performance, effectively preventing water infiltration (3).

4.2.2 Construction Technology of Composite Geomembrane Seepage Control

The construction technology of composite geomembrane seepage control mainly includes the following steps:

1. Construction Preparations:
   • Material preparation: Inspect the composite geomembrane delivered to the site to ensure its quality meets design requirements
   • Equipment preparation: Prepare welding equipment, anchoring tools, and other construction equipment
   • Base treatment: Clean and treat the dam surface to ensure it is 平整 and free of sharp objects (3)
2. Composite Geomembrane Laying:
   • Lay the composite geomembrane in a certain direction according to design requirements
   • Leave a certain amount of slack during laying to adapt to dam deformation
   • Avoid wrinkles, twists, and other phenomena during the laying process (3)
3. Joint Treatment:
   • Joints can be treated by heat welding or gluing
   • Heat welding method: Use a heat welding machine to heat and melt the edges of two membranes for connection, forming a continuous seepage control layer
   • Gluing method: Use special adhesive to bond the edges of two membranes together
   • Strictly inspect joints to ensure no seepage (3)
4. Anchoring Treatment:
   • The perimeter of the composite geomembrane should be anchored to prevent membrane displacement
   • Anchoring methods can adopt trench anchoring, expansion bolt anchoring, etc.
   • Anchor points should be evenly distributed, and anchoring should be firm and reliable (3)
5. Protective Layer Construction:
   • After the composite geomembrane is laid, promptly construct the protective layer
   • Protective layer materials can use soil, sand and gravel, concrete slabs, etc.
   • Protective layer construction should avoid causing damage to the membrane (3)

4.2.3 Advantages and Disadvantages Analysis of Composite Geomembrane Seepage Control

Advantages:

1. Good Seepage Control Performance: The composite geomembrane has a low permeability coefficient and remarkable seepage control effect
2. Strong Deformation Adaptability: Has good flexibility and anti-deformation ability, can adapt to dam deformation
3. Simple Construction: Construction technology is relatively simple, and construction speed is fast
4. Light Weight: Compared with seepage control materials such as concrete and asphalt concrete, it is light in weight, convenient for transportation and construction
5. Low Cost: Under the premise of meeting the same project quality, the cost is relatively low
6. Convenient Maintenance: If seepage is detected, repair is relatively easy (3)

Disadvantages:

1. Limited Puncture Resistance: Although improved compared to single geomembrane, it is still not as good as the PVC seepage control system
2. Durability Inferior to PVC: Long-term exposure to sunlight is prone to aging, with a relatively short service life
3. High Construction Requirements: Laying and welding quality directly affect the seepage control effect, with high construction requirements
4. Greatly Affected by Weather Conditions: Construction is difficult under harsh weather conditions such as low temperature and rain
5. High Protection Requirements: Need to set up a complete protective layer, otherwise vulnerable to external factors
6. Complex Joint Treatment: Joints are weak points of seepage control, improper treatment easily leads to seepage (3)

4.3 Comprehensive Comparison of Different Seepage Control Technologies

The following table comprehensively compares PVC seepage control, asphalt concrete seepage control, and composite geomembrane seepage control technologies:

 

Comparison Item	PVC Seepage Control Technology	Asphalt Concrete Seepage Control Technology	Composite Geomembrane Seepage Control Technology
Seepage Control Performance	Excellent, permeability coefficient ≤10-12cm/s	Good, permeability coefficient ≤10-8cm/s	Good, permeability coefficient ≤10-11cm/s
Deformation Adaptability	Strong, can adapt to large deformations	Strong, can adapt to certain deformations	Medium, can adapt to general deformations
Material Durability	Long, can reach more than 50 years	Medium-long, about 30 years	Medium, about 20-30 years
Construction Difficulty	High, strict technical requirements	High, complex technology	Medium, relatively simple construction
Construction Period	Short, fast construction speed	Long, many construction procedures	Short, fast construction speed
Climate Adaptability	Good, can be constructed within a wide temperature range	Poor, difficult construction in low-temperature environments	Medium, greatly affected by extreme weather
Engineering Cost	Higher	High, about 70% of concrete seepage control	Lower
Maintenance Cost	Low, less post-maintenance work	High, regular maintenance needed	Medium, regular inspection and repair needed
Applicable Conditions	High dams, projects with large deformations	Medium-low dams, projects with small deformations	Small and medium-sized projects, projects with little deformation
Application in Jiangpinghe	Adopted above elevation 380m of the dam, with remarkable effects	Not adopted	Not adopted

Through comparison, it can be seen that each of the three seepage control technologies has its own advantages and disadvantages. PVC seepage control technology has obvious advantages in terms of seepage control performance, deformation adaptability, and material durability, especially suitable for application in high dams and projects with large deformations; although asphalt concrete seepage control technology has good seepage control performance, its construction technology is complex, construction period is long, and cost is high; composite geomembrane seepage control technology has low cost and simple construction, but has certain risks when applied in high dams and projects with large deformations.

As a 219-meter-high concrete face rockfill dam, the Jiangpinghe Hydropower Station's choice to adopt PVC seepage control technology to enhance dam seepage control is a reasonable decision, and its application effect has also proven this point. Under the condition of a reservoir water level at elevation 460m, the total seepage volume after adopting the PVC seepage control system is only 5.3L/s, demonstrating remarkable seepage control effects (1).

V. Domestic and Foreign Standards and Specifications for PVC Seepage Control Technology

5.1 Relevant National Standards

PVC seepage control technology in China has a complete standard system, mainly including the following national standards:

1. "Geosynthetics - Polyvinyl Chloride Geomembrane" (GB/T 17688-1999):
   • This standard specifies the classification, naming, technical requirements, test methods, inspection rules, marking, packaging, transportation, storage, etc. of polyvinyl chloride geomembranes
   • Applies to geomembranes formed by calendering or extrusion using polyvinyl chloride resin as the main raw material with appropriate additives
   • Has been abolished on December 15, 2017 (7)
2. "Geosynthetics - Nonwoven Composite Geomembrane" (GB/T 17642-2008):
   • This standard specifies the product classification, specifications, code names, technical requirements and quality evaluation, test methods, inspection rules, packaging, marking, storage and transportation, etc. of nonwoven composite geomembranes
   • Applies to nonwoven geotextiles as the base material, polyethylene, polyvinyl chloride, etc. as the membrane material, formed by calendering, coating, rolling, etc. of nonwoven composite geomembranes
   • Is currently the main national standard for composite geomembranes (7)
3. "Technical Specifications for Polyethylene (PE) Geomembrane Seepage Control Engineering" (SL/T 231-2020):
   • This specification specifies the design, construction, quality inspection and acceptance, etc. of polyethylene geomembrane seepage control projects
   • Although mainly targeting polyethylene geomembranes, some principles and methods can also be referenced for PVC seepage control projects
   • Is an important technical specification in the water conservancy industry (7)
4. "Technical Code for Application of Geosynthetics" (GB/T 50290-2014):
   • This code specifies the application technical requirements of geosynthetics in geotechnical engineering
   • Includes material selection, design methods, construction technology, quality control, etc.
   • Is a general standard for the application of geosynthetics (7)
5. "Technical Specifications for Application of Geosynthetics in Water Conservancy and Hydropower Engineering" (SL/T 225-2020):
   • This specification specifies the application technical requirements of geosynthetics in water conservancy and hydropower engineering
   • Includes seepage control, filtration, drainage, reinforcement and other application areas
   • Is an important specification for the application of geosynthetics in water conservancy and hydropower engineering (7)

Although GB/T 17688-1999 "Geosynthetics - Polyvinyl Chloride Geomembrane" has been abolished, PVC seepage control technology can still refer to the relevant provisions of the above other standards.

5.2 Technical Specifications Followed in Jiangpinghe Project

During the design, construction and acceptance of the PVC seepage control project in Jiangpinghe Hydropower Station, the following technical specifications were mainly followed:

1. "Technical Code for Joint Waterstop of Concrete Face Rockfill Dam" (DL/T 5115-2008):
   • This code specifies the design, materials, construction and acceptance requirements for joint waterstops of concrete face rockfill dams
   • The design and construction of PVC gaskets for the Jiangpinghe Hydropower Station strictly follow the requirements of this code (1)
2. "Technical Specification for Waterstop Belts of Hydraulic Structures" (DL/T 5215-2005):
   • This specification specifies the classification, specifications, technical requirements, test methods, inspection rules, etc. for waterstop belts of hydraulic structures
   • The design and construction of the PVC seepage control system for the Jiangpinghe Hydropower Station refers to the requirements of this specification for the waterstop belts (1)
3. "Technical Code for Application of Geosynthetics" (GB/T 50290-2014):
   • This code specifies the application technical requirements of geosynthetics in geotechnical engineering
   • The design and construction of the PVC seepage control system for the Jiangpinghe Hydropower Station follow the basic principles of this code (1)
4. "Technical Specifications for Application of Geosynthetics in Water Conservancy and Hydropower Engineering" (SL/T 225-2020):
   • This specification specifies the application technical requirements of geosynthetics in water conservancy and hydropower engineering
   • The design and construction of the PVC seepage control system for the Jiangpinghe Hydropower Station refers to the relevant requirements of this specification (1)
5. "Technical Code for Concrete Cutoff Wall Construction in Hydraulic and Hydropower Engineering" (DL/T 5199-2014):
   • This code specifies the design, construction, quality inspection and acceptance, etc. for concrete cutoff walls
   • The connection part between the PVC seepage control system and the concrete cutoff wall of the Jiangpinghe Hydropower Station refers to the requirements of this code (1)

In the PVC seepage control project of the Jiangpinghe Hydropower Station, particular attention was also paid to the following points:

1. Material Quality Control: All performance indicators of the PVC composite geomembrane meet design requirements and relevant standard provisions
2. Construction Technology Control: Strictly follow design and specification requirements for base treatment, membrane laying, welding, anchoring and other construction operations
3. Quality Inspection Control: Use a variety of inspection methods to monitor construction quality throughout the process, ensuring that all indicators meet requirements
4. Acceptance Standard Control: Accept according to relevant standards and design requirements, ensuring that project quality meets expectations (1)

5.3 International Standards for PVC Seepage Control Technology

PVC seepage control technology also follows corresponding international standards in international applications, mainly including the following:

1. ASTM D7176-06(2018) Standard Specification for Non-Reinforced Polyvinyl Chloride (PVC) Geomembranes Used in Buried Applications:
   • This standard specifies the technical requirements for non-reinforced polyvinyl chloride (PVC) geomembranes used in buried applications
   • Applies to PVC sheets with a thickness of 0.25mm to 1.5mm (0.010 inches to 0.060 inches), typically used for geomembrane linings
   • Specifies requirements for materials, sheets, test methods, workmanship criteria, and marking methods (7)
2. EN 13967:2012+A1:2017 Flexible Sheets for Waterproofing - Plastic and Rubber Damp Proof Sheets Including Plastic and Rubber Basement Tanking Sheet - Definitions and Characteristics:
   • This European standard specifies the definitions and characteristics of flexible plastic and rubber sheets intended for use as damp-proofing in buildings, including basement tanking
   • Specifies requirements and test methods, and provides for the evaluation of conformity of products with the requirements of this standard
   • Applies to flexible plastic and rubber sheets used for waterproofing and moisture-proofing in building construction (34)
3. ISO 10319:2019 Geotextiles and Geotextile-Related Products - Determination of Tensile Properties:
   • This international standard specifies the method for determining the tensile properties of geotextiles and geotextile-related products
   • Provides a basis for testing the tensile strength and elongation of PVC geomembranes (25)
4. ASTM D7408 Standard Specification for PVC Geomembrane Factory and Field Seams:
   • This standard specifies the technical requirements for PVC geomembrane factory and field seams
   • Provides standards for welding quality control of PVC geomembranes (26)

International standards have strict regulations on the material performance, testing methods, and construction technology of PVC geomembranes, providing a basis for the international application of PVC seepage control technology. The design and construction of PVC seepage control projects in the Jiangpinghe Hydropower Station refer to the relevant requirements of these international standards while meeting national standards.

VI. International Case Studies of PVC Membrane Seepage Control Technology

6.1 Case Study of Miel I Dam in Colombia

6.1.1 Project Overview

The Miel I Hydropower Development Project includes an 188-meter-high RCC dam, currently the tallest RCC dam in the world. The dam is located in a hot and rainy region of Colombia, with significant challenges for seepage control (1).

6.1.2 Application of PVC Membrane Seepage Control Technology

The impervious face system of the Miel I dam consists of a combination of a strip of grouted enriched RCC and a PVC membrane, both along the vertical upstream face of the dam. This design effectively prevents seepage through the dam body (1).

The PVC membrane used in the Miel I dam project has excellent flexibility and impermeability, able to adapt to the deformation of the dam body while providing a reliable seepage control barrier. The membrane is connected to the dam foundation through a water-stop system to ensure a complete seepage control system (1).

6.1.3 Implementation Effect

The overall seepage control effect of the Miel I dam is highly satisfactory. After impoundment, the total leakage through the dam body is less than 2.5 L/s, demonstrating the excellent seepage control performance of the PVC membrane (1). According to instrumentation data, this leakage enters the dam through the foundation upstream of the grout curtain, indicating that the PVC membrane on the dam face effectively prevents seepage through the dam body (1).

The successful application of the Miel I dam provides valuable experience for the application of PVC membrane seepage control technology in ultra-high dams, proving that PVC membrane has broad application prospects in high dam seepage control projects.

6.2 Case Study of Kadamparai Dam in India

6.2.1 Project Overview

The Kadamparai dam is located in India and had experienced serious seepage problems before reinforcement. The leakage rate increased significantly after repair attempts using traditional methods failed (19).

6.2.2 Application of PVC Membrane Seepage Control Technology

In 2003, the Tamil Nadu Electricity Board (TNEB) internationally tendered for the installation of a drainage geomembrane system on the upstream face of the dam. The Swiss company CarpiTech SA won the contract and began on-site seepage control work on January 17, 2005 (19).

The seepage control system uses a 2000g/m² non-woven needle-punched geotextile as the first layer, installed on the original masonry surface and fixed with small anchors to prevent the seepage control lining from being punctured. The seepage control lining is a Sibelon CNT 3750 type geocomposite material, consisting of a 2.5mm thick PVC geomembrane laminated onto a 500g/m² polyester geotextile during extrusion, supplied in rolls long enough to cover the dam face without transverse seams (19).

The PVC geocomposite material is anchored to the dam face using the Carpi patented system, which consists of two stainless steel pressure strips (U-shaped and 形 - shaped) that can pre-tension and fasten the geocomposite material. The U-shaped steel is directly installed on the originally exposed surface with a center-to-center spacing of 5.7m. The PVC geocomposite material is perforated according to the spacing and diameter of the fixing piles and fastened to the U-shaped steel with 形 - shaped steel. These steel strips are covered with a 2.5mm thick Sibelon C 3250 PVC geomembrane strip, which is heat-welded to the PVC geocomposite material for seepage control (19).

6.2.3 Implementation Effect

The Kadamparai dam seepage control project was completed on May 2, 2005. According to TNEB reports, the installation of the exposed PVC geocomposite material performed better than expected, with seepage volume decreasing from 3×10⁴ L/min to 1×10² L/min, demonstrating significant seepage control effects (19).

The successful application of the Kadamparai dam proves that PVC membrane seepage control technology has significant advantages in the reinforcement of existing dams, especially for dams with complex conditions and serious seepage problems.

6.2 Case Study of Taissir Dam in Mongolia

6.2.1 Project Overview

The Taissir Hydropower Station project in Mongolia is located on the Ulaanbum Canyon of the Zabkhan River at the junction of Gobi Altai and Zavkhan provinces, approximately 1050km west of Ulaanbaatar, the capital of Mongolia (18). The dam site has an original riverbed elevation between EL1600m and EL1700m, with a sand and gravel overburden layer 4-5m thick.

The dam is a roller compacted concrete (RCC) dam with a total height of 50m above the riverbed, a crest length of approximately 190m, and a dam volume of about 200,000m³. After completion, the dam forms a reservoir with a water surface area of 50km² and a storage capacity of about 930 million cubic meters (18).

The climate in the project area is characterized by extremely cold winters and hot summers, with an annual average temperature of 0°C, extreme temperature values of -51°C in January and +39°C in July, and large diurnal temperature variations. The annual precipitation in the region is only 200mm, with northwest and north winds as the main wind directions, and frequent sandstorms in April and May (18).

6.2.2 Application of PVC Membrane Seepage Control Technology

The dam seepage control system consists of a single-row grouting impervious curtain and a dam face impervious membrane. The curtain grouting is constructed on a grouting platform cast close to the upstream face of the dam, with a maximum rock penetration depth of 35m. The dam face impervious membrane is anchored at the bottom on the grouting platform and at the top on the normal concrete (0.4m thick) above the RCC. The impervious membrane in the intake tower and spillway dam sections is anchored on the corresponding normal concrete (18).

The dam face impervious membrane uses flexible polyvinyl chloride (PVC) material bonded to a thermally adhesive, non-woven, needle-punched polyester geotextile, with sufficient flexibility; it can be field-welded at temperatures up to 40°C; it can resist ultraviolet radiation; it can resist erosion in the humid alkaline environment inside the dam, as well as deterioration from organic matter and bacterial growth (18). The minimum thickness of the PVC for the exposed membrane is 2.5mm, and the minimum thickness of the PVC for the internal lining membrane is 1.6mm.

The installation of the impervious membrane was subcontracted to the Swiss company CarpiTech SA, with 7 management and construction technical personnel on-site, working 协同 with 1 foreman, 1 technician, and 8 laborers from our side. The impervious membrane installation construction started on June 11, 2007, and was completed on September 1, 2007, completing a total of 8135m² of impervious membrane installation, more than a month ahead of schedule (18).

6.2.3 Implementation Effect

The successful application of PVC membrane seepage control technology in the Taissir Dam in Mongolia has fundamentally solved the technical problem of concrete seepage control in high-cold regions, representing a bold technological innovation (18). The dam has been operating well since completion, with the impervious membrane effectively preventing seepage and ensuring the safe operation of the dam.

This case demonstrates that PVC membrane seepage control technology has significant advantages in harsh environments, especially in high-cold regions with large temperature differences, providing valuable experience for the application of PVC membrane seepage control technology in similar environments worldwide.

VII. Conclusion and Recommendations

7.1 Application Effect of PVC Seepage Control Technology in Jiangpinghe Project

The application of PVC seepage control technology in the Jiangpinghe Hydropower Station project has achieved remarkable results, mainly manifested in the following aspects:

1. Significant Seepage Control Effect: Under the condition of a reservoir water level at elevation 460m, the total seepage volume through the PVC seepage control system below elevation 382m (corresponding to a maximum water head of 197m) is only 5.3L/s, compared with 13.2L/s without the geomembrane reinforcement, demonstrating a significant seepage control effect (1).
2. Significant Economic Benefits: The project saved 10.27 million yuan in engineering investment and created economic benefits of 16 million yuan. Meanwhile, the application of PVC seepage control technology has also reduced post-maintenance costs, with long-term economic benefits (1).
3. Adaptability to High Dam Deformation: As a 219-meter-high face slab rockfill dam, the Jiangpinghe Hydropower Station will experience certain deformation during operation. The PVC seepage control system, with its good flexibility and deformation adaptability, can effectively adapt to dam deformation without 破裂，ensuring the stability of the seepage control effect (1).
4. Controllable Construction Quality: Through strict construction management and quality control, the construction quality of the PVC seepage control project in the Jiangpinghe Hydropower Station has been effectively guaranteed, with all indicators meeting design requirements and relevant standard provisions (1).
5. Technological Innovation Application: The PVC seepage control project in the Jiangpinghe Hydropower Station has carried out multiple technological innovations in design and construction, such as using 2.5mm thick PVC composite geomembrane and optimizing the anchor system design, providing valuable experience for the application of high dam PVC seepage control technology (1).
6. Engineering Demonstration Role: The successful application of the PVC seepage control project in the Jiangpinghe Hydropower Station provides important reference for the seepage control design and construction of similar high dam projects, with significant engineering demonstration effects (1).

These achievements indicate that PVC seepage control technology has broad application prospects in high dam projects, especially in projects with complex geological conditions and high deformation requirements, where the advantages of PVC seepage control technology are more obvious.

7.2 Applicability and Limitations of PVC Seepage Control Technology

PVC seepage control technology has broad applicability, but also has certain limitations, mainly manifested in:

Applicability:

1. High Dam Projects: Particularly suitable for high dam projects above 200 meters, such as the 219-meter-high face slab rockfill dam of the Jiangpinghe Hydropower Station.
2. Projects with Large Deformations: Suitable for dam bodies that may undergo large deformations, such as face slab rockfill dams and earth-rock dams.
3. Projects with High Seepage Control Requirements: Projects with extremely high seepage control requirements, such as reservoirs, storage tanks, and wastewater treatment tanks.
4. Regions with Moderate Climate Conditions: Suitable for regions with relatively mild climate conditions, and special measures need to be taken in extreme climate conditions.
5. Regions with Complex Geological Conditions: Suitable for regions with complex geological conditions, such as areas with faults and fissures. (1)

Limitations:

1. Temperature Sensitivity: PVC material is relatively sensitive to temperature changes, and its performance may be affected under extreme temperature conditions.
2. High Construction Requirements: The construction technology of the PVC seepage control system has high requirements, and construction quality directly affects the seepage control effect.
3. Material Durability: Although PVC material has good durability, long-term exposure to sunlight or contact with chemical substances may lead to aging.
4. High Requirements for Foundation: The PVC seepage control system has high requirements for the flatness of the foundation surface, and strict base treatment is needed.
5. Difficult Repair: Once seepage occurs, repair is more difficult and requires professional technology and equipment.
6. High Material Cost: Compared with other seepage control materials, the cost of PVC materials is higher, with a larger initial investment. (3)

In practical applications, the applicability and limitations of PVC seepage control technology should be comprehensively considered according to the characteristics and conditions of the project, and the most suitable seepage control plan should be selected. For high dams, projects with large deformations, and projects with high seepage control requirements, PVC seepage control technology is an ideal choice; while for low dams, projects with small deformations, and projects with limited budgets, other seepage control technologies can be considered.

7.3 Recommendations for Future Development

Based on the successful experience of the PVC seepage control technology application in the Jiangpinghe Hydropower Station project and the current development status of PVC seepage control technology, the following recommendations for future development are proposed:

1. Strengthen Material Research and Development:
   • Develop new PVC materials with better aging resistance, high and low temperature resistance, and chemical corrosion resistance
   • Improve the strength and toughness of PVC materials, enhancing their deformation adaptability
   • Develop environmentally friendly PVC materials to reduce environmental impact (3)
2. Improve the Standard System:
   • Accelerate the formulation of special standards for PVC composite geomembranes
   • Improve the design, construction, testing, and acceptance standards for PVC seepage control systems
   • Develop application guidelines for PVC seepage control technology under different environmental conditions (7)
3. Innovative Design Methods:
   • Research the design theory and methods for PVC seepage control systems for high dams
   • Develop combined design methods for PVC seepage control systems and other seepage control structures
   • Optimize the design of PVC seepage control systems using numerical simulation technology (1)
4. Improve Construction Technology:
   • Develop PVC seepage control construction technologies suitable for different conditions
   • Develop efficient and precise PVC membrane welding equipment and technology
   • Research construction technologies for adverse conditions such as low temperature and rain (12)
5. Strengthen Quality Control:
   • Improve the quality control system for PVC seepage control systems
   • Develop advanced quality testing technologies and equipment
   • Establish long-term monitoring systems for PVC seepage control projects (12)
6. Promote Engineering Applications:
   • Summarize the successful experience of PVC seepage control projects for high dams
   • Carry out training and exchange activities for PVC seepage control technology
   • Promote the application of PVC seepage control technology in more fields (1)

Through the above measures, the performance and application level of PVC seepage control technology can be further improved, making it play a greater role in water conservancy and hydropower engineering, environmental protection engineering, and other fields. Especially in high dam projects, PVC seepage control technology has broad application prospects and is worthy of further research and promotion.

The successful application of the PVC seepage control project in the Jiangpinghe Hydropower Station provides valuable experience for the development of PVC seepage control technology. In the future, with the continuous progress of materials science, manufacturing technology, and engineering technology, PVC seepage control technology will show stronger vitality and application value.

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[32] EN 13967 Flexible Sheets for Waterproofing - Plastic and Rubber Moisture Resistant Sheets, Including Plastic and Rubber Base Tank Sheet https://www.laboratuar.com/en/testler/malzeme-testleri/testler/malzeme-testleri/en-13967-su-yalitimi-icin-esnek-levhalar---plastik-ve-kaucuk-temel-tank-levhasi-dahil-plastik-ve-kaucuk-neme-dayanikli-levhalar/

[33] 塑料防水膜EN 13967认证标准解析:性能要求和检测流程 https://m.11467.com/blog/d9652706.htm

[34] EN 13967:2012+A1:2017 防水柔性板-包括塑料和橡胶底层制箱用薄板的塑料和橡胶防潮薄板-定义及性能 发布历史 https://m.antpedia.com/standard/7802272-9.html

[35] 两分钟分享防水膜EN 13859 CE认证咨询|ce|en|塑料|欧盟|防水膜_手机网易网 http://m.163.com/dy/article/JKNSAGLR0552K7WB.html

[36] ASTM International - ASTM D7176-06(2018) - Standard Specification for Non-Reinforced Polyvinyl Chloride (PVC) Geomembranes Used in Buried Applications | GlobalSpec https://standards.globalspec.com/std/13000016/ASTM%20D7176-06(2018)

[37] PVC Flexible Geomembrane - Geofantex https://geofantex.com/pvc-flexible-geomembrane.html

[38] PVC Mechanical Properties | EPI https://www.geomembrane.com/technical-info/pvc/pvc-mechanical-properties.html

[39] HDPE/PVC Flame-Retardant Geomembrane - with Good Flame Retardant Performance, Used for Anti-Seepage - Building Material, PVC Sheet | Made-in-China.com https://m.made-in-china.com/amp/product/HDPE-PVC-Flame-Retardant-Geomembrane-with-Good-Flame-Retardant-Performance-Used-for-Anti-Seepage-2121320435.html

[40] Geomembrane physical properties - Professional geomembrane and geotextile manufacturer https://tinhygeomembrane.com/geomembrane-physical-properties/

[41] Insulating films - Ergis https://ergis.eu/en/contents/customers/insulating-films

[42] Protan HydraPlan membrane https://www.protan.com/roofing-membranes/pvc-roofing-membranes/protan-hydraplan/

[43] DIN EN 13967 - Flexible sheets for waterproofing - Plastic and rubber damp proof sheets including plastic and rubber basement tanking sheet - Definitions and characteristics (includes Amendment :2017) | GlobalSpec https://standards.globalspec.com/std/10181529/din-en-13967

[44] (PDF) Ten-year PVC geomembrane durability https://www.researchgate.net/publication/239410389_Ten-year_PVC_geomembrane_durability

[45] Specifications for Thermal Welding PVC https://www.geomembrane.com/technical-info/pgi-technical-bulletins/specifications-for-thermal-welding-pvc-geomembranes.html

[46] Geomembrane Thickness | EPI https://www.geomembrane.com/technical-info/pvc/minimum-geomembrane-thickness.html

[47] BSI - BS EN 13967 - Flexible sheets for waterproofing - Plastic and rubber damp proof sheets including plastic and rubber basement tanking sheet - Definitions and characteristics | GlobalSpec https://standards.globalspec.com/std/10196479/BS%20EN%2013967

[48] DIN EN 13967 https://www.en-standard.eu/din-en-13967-flexible-sheets-for-waterproofing-plastic-and-rubber-damp-proof-sheets-including-plastic-and-rubber-basement-tanking-sheet-definitions-and-characteristics-includes-amendment-2017/

[49] BS EN 13967 - Flexible sheets for waterproofing. Plastic and rubber damp proof sheets including plastic and rubber basement tanking sheet. Definitions and characteristics https://landingpage.bsigroup.com/LandingPage/Undated?UPI=000000000030150490

[50] EN 13967:2012+A1:2017 - Flexible sheets for waterproofing - Plastic and rubber damp proof sheets https://standards.iteh.ai/catalog/standards/cen/4aec09e9-4f4a-4f65-99a1-cac712ba91e0/en-13967-2012a1-2017

[51] PVC waterproofing for deck type roofs | DANOPOL+ HS 1.5 https://www.danosa.com/global/product/danopol-hs-1-5-2/

[52] PVC fabricated geomembrane for landfill applications https://www.geomembrane.com/technical-info/geomembrane-research/utilizing-pvc-geomembranes-for-landfill-and-pond-liners.html

[53] PVC Geomembrane Components EPI - The Liner Company https://www.geomembrane.com/technical-info/pgi-technical-bulletins/identification-and-behavior-of-pvc-geomembrane-components.html

[54] An open solicitation to work on development of a new GSI specification for EIA geomembrane - Geosynthetics Magazine https://geosyntheticsmagazine.com/2022/08/01/an-open-solicitation-to-work-on-development-of-a-new-gsi-specification-for-eia-geomembrane/

[55] Geomembrane definition https://biogasmembrane.com/geomembrane/